Power transmission for machine tools



POWER TRANSMISSION FOR MACHINE TOOLS Filed Jan. 26, less 2 Sheets-Sheet; 1

FIG. 2

INVENTOR RAYMOND C. GRIFFITH ATTORNEY May 11', 1943. GRIFFITH 2,318,851-

POWER TRANSMISSION FOR MACHINE TOOLS OR RAYMOND C. GRIFFITH BY I/V ATTORNEY Patented May 11, 1943 2,318,851 POWER. TRANSMISSION FOR MACHINE TOOLS.

Raymond C. Grifilth, Detroit, Mich.,asslgnor to Vickers Incorporated, Detroit, Mich., a corporation oi! Mich nn Application January 26, 1938, Serial No. 186,924 3 Claims. (CI. 77-28) This invention relates to power transmissions and more particularly to those of the fluid type wherein a power transmitting fluid, such as oil. and hereinafter referred to as such, is utilized for the transmission of power between one or more pumps and one or more fluid motors.

The invention is particularly concerned with the provision of such a power transmission systern which is particularly adapted for use in connection with a radial drill for the purpose of actuating the drill-arm up and down on the column and for translating the drill head in and out on the arm as well as for operating clamping 'mechanisms for the arm and for the swivel mechanism of the column;

It has. been proposed heretofore to operate the elevating and traversing mechanisms and the clamps ofa radial drill under hydraulic con trol. One of the difllculties presented is that of providing a safe and yet satisfactory means for elevating and lowering the arm on the column. The arm and mechanism carried thereby on a large radial drill weighs several hundred pounds and it is of prime importance that the possibility of the arm falling from an elevated position due to failure of any portionof the mechanism be avoided entirely. Where the arm is elevated by fluid pressure exerted in a piston and cylinder motor directly connected with the arm, there is ever present the possibility that the fluid pres; sure may fail due to rupture of a. pipe orsticking of a valve and thus permitting the arm to fall suddenly with its attendant haza d to the operator. This possibility has bee avoided heretofore in hydraulically controlled radial drills by utilizing a conventional power driven screw and nut elevating mechanism together with, suitable hydraulic clutches for controlling the application of-power to the elevating mechanism in either direction. Radial drills of this character have been unsatisfactory, however, due to the a rotary fluid motor for actuating the same and suitable valve mechanism for operation of the fluid motor. In addition, 'means are provided for preventing operation of the fluid motorwhenever a predetermined amount of wear has oc-' curred in the screw and nut mechanism of'the elevating gear.

A further object is to provide a power transmission system for a radial drill wherein simple and reliable interlocking means are provided for insuring that the arm is clamped whenever the elevating mechanism is stopped and that the arm is unclamped before the elevating mechanism is started.

A further objectis to provide a power transmission system wherein a plurality of fluid motors are operated from a single pump under independent control valves and wherein means for by-passing the pump is provided, which means are under the simultaneous control of all of the certain of the motors.

difliculty of obtaining precise control of the stop ping position of the arm in its elevation without unduly sacrificing rapidity of operation when the arm has to be elevated or lowered a con-- siderable distance in one traverse.

It is,' accordingly, an object of the present invention to provide a hydraulically operated elevating mechanism for a radial drill which is not only absolutely safe against the possibility of dropping the arm but is also capable of rapidly. elevating or lowering the arm as well as precisely controlling the stopping position. This and other objects are achieved by utilizing a screw and nut elevating mechanism together with It is also an object to provide a power transmission for a radial drill having an arm elevating motor, a head traversing motor, a column clamping motor: and an arm clamping motor wherein individual control valves are provided for operating any of the motors selectively from a common pump and wherein means is provided for by-passing the pump only when no fluid is required for operation of any of the motors and to prevent by-passing whenever the arm is unclamped.

A'f-urther object is to provide a power transmission of the character described wherein the column clamping control valve may be left in clamping or unclamping positionand wherein means' responsive to operation of, the column clamping motor is provided forcontrolling the by-passing of the pump.

Furtheroblects and advantages of the present D invention will be apparentfrom the following description, reference being had to the accompanying drawings wherein a. preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a side elevation of the radial drill incorporating the preferred form of the present invention.

Fig. 2 is, a detail sectional view through a portion of the elevating mechanism for the arm.

Fig. 3 is a fragmentary view showing the column clamping motor. r

umn clamping mechanism.

Fig. 5 is a diagrammatlcal view showing the hydraulic circuits incorporated in the drill press of Fig. 1.

Referring to Fig. 1, there is shown a drill press comprising a base I having an upright column l2 secured thereto upon which, is rotatably mounted a sleeve I4. Slidably mounted on the sleeve I 4 is an arm I6 upon which is mounted a translatable head I8 having the usual motor and spindle together with the necessary controls. Sleeve I4 is provided with an enlarged part 20 at its lower end which is split at 22 (Fig: 4). A clamping bolt 24 carries a block 28 at one end which is engaged and an eccentric crank 28 formed on a clamping shaft 30, pivoted in bearings 32 at the top and bottom of the sleeve I4. The other end of the bolt 24 carries an adjustable nut 34, for engagement with a flange 36 adjacent the slot 22.

The shaft 30 is provided with a longitudinal keyway and carries slidably but non-rotatably secured thereto a pinion 38 (Fig. 3) which engages with a rack 40 formed on the stem of a piston and cylinder fluid motor 42. It will be seen that actuation of the motor 42 will rotate the pinion 38 through the rack 40 and as a consequence rotates the shaft 30, which, acting through the crank 28 and block 26 will cause the nut 34 to clamp the adjacent sides of slot 22 closely together to prevent the sleeve I4 from rotating on the column I2.

The arm I6 is provided with a slot 44 in a manner analogous to the large portion 20 of the sleeve I4. Suitable clamping levers 46 act through clamping bolts to close the slot and clamp the arm to the sleeve whenever the adjacent levers 46 are moved to the left in Fig. 1. A piston and cylinder fluid motor 50 has a stem 52 engageable with the ends of the levers 46 for this purpose, the arrangement being such that a toggle action is provided whereby the arms 46 when once moved thereto remain in clamped position, without maintaining fluid pressure in the motor 50.

Mounted on the arm is an electric motor 54 for operating a pump 56 (Fig. for supplying fluid to the motors 42 and as well as to a rotary fluid motor 58 and a second rotary fluid motor 60. The motor 58 is connected by gearing 62 (Fig. 1) to a head traversing screw 64 mounted in suitable bearings on the arm I0 and operating in a suitable nut secured to the head I8. The motor 80 is connected by gearing 66 to an elevating nut 58 (Fig. 2) mounted in the arm i5 and supporting the same on anti-friction thrust bearings I0. The nut 58 is threaded on a stationary elevating screw 12 secured to a sleeve M.

The motor 60 is also connected by gears 14 to an auxiliary nut "I6 threaded on the screw I2 and urged upwardly relative to the nut 58 by a spring 18 abutting against the bottom wall of the arm I6. It will be seen that the weight of the arm It holds the nut 68 with the bottom surface of its threads always in contact with the upper surface of the threads on the screw I2. The nut. I6, however, is urged by the spring 18 upwardly so that the upper surface of its threads are always in contact with the bottom surface of the threads on the screw I2. Consequently, as wear occurs in the threads of both the screw I2 and the nut 68 or of either of them, the nut I6 will move upwardly relative to the nut50 and arm I6. The nut I6 is thus responsive to wear occurring in the threads of the elevating mechanism.

- made.

A two-way pilot valve is mounted on the arm and has a stem 82 connected to the lever 34, the right hand end of which is urged lightly into contact with the top surface of the nut I5 by a spring within the valve 80. The valve 80 is so adjusted that whenever wear has occurred in the threads of the elevating mechanism sufiicient to render them liable to strip, the valve will open communication between its two ports.

Control of the fluid motors 42 and 50, 58 and $0 is exercised through a unitary control panel 85 mounted on the front of the arm and having 3 operating handles 88, and 92. Referring now to Fig. 5, the hydraulic circuits connecting the pump 55, the panel 86 and the respective fluid motors are there illustrated. A tank 94, which may be provided in a hollow portion of the arm I5, contains a supply of oil which may be withdrawn through a suction conduit 06 by the pump 55. The latter delivers oil to the panel through a conduit 98 having a branch I00 to the elevating motor 60. A drain conduit I00 connects the casings of motors 58 and 60 with the tank 84. A tank conduit IIO connects with ports H2, H4 and H0 of the valve I06 and also with ports H8 and I20 of the valve I08. Ports I22 and I24 of the valve I06 connect, a conduit I 26 with the tank ports I I4 and I I0 whenever a valve spool I28 is in the center position as illustrated. When the spool I28 is moved downwardly port I22 connects to pressure port I04 while port I24 is cut off from tank port; II6. Whenthe spool I28 is moved upwardly port I24 connects to pressure port I04 while port I22 is cut ofi from tank port H4.

Ports I30 and I32 connect a conduit I34 with the pressure port I02 when the valve spool I28 is in the center position. When the spool is moved upwardly port I30 is cut cii from port I02 and connected to tank port I I2. When the spool whenever pressure in the conduit I26 is below a predetermined value, which is above the pressure required normally to move the motor 50 into unclamping position. At any pressure above this valve 136 opens permitting oil to flow into port I38 and through a conduit I40 to the pressure port I42 of the valve I08.

The latter has a pair of ports I44 and I46 which are connected to the tank ports H8 and I20 when a valve spool I48 is in the center position as shown. When the spool is moved upwardly port I44 remains connected to port I20 while port I46 is cut off from port .I I8 and connected to pressure port I42. When the spool is moved downwardly opposite connections are The ports I44 and I46 connect by conduits I50 and I52 with the opposite sides of the fluid motor 50. The valve I08 also has a pair of ports I54 and I56 which are connected together when the spool I48 is in center position, but

is moved upwardly or downwardly.

The spools I20 and I48 are connected together as shown at I58 for simultaneous operation by the control lever 90. Suitable centering springs I60 and I82 return the spools to center position whenever the handle 90 is released.

The pressure conduit 98 has a branch I64 connecting to a port I66 of a valve I68 which controls operation of the column clamping motor 42. The valve is provided with a pair of ports. I69 and I which are normally connected to tank ports I12 and I14 when the spool I16 is in center position. When the spool is moved upwardly, port I69- remains connected to tank ports I12 while port I10 is cut off from return port I14 and connected to pressure port I66. When the spool is moved downwardly the opposite connections are made. The valve I68 is also provided with a pair of ports I18 and I80 which are normally connected together in the center position and cut ofi from each other when the spool is moved either upwardly or downwardly.

A- conduit I82 remains connected 'with both ports I18 and I80 in the center position, with the port I18 only when the valve is moved upwardly and with the port I80 only when the valve is moved downwardly. Conduits I84 and I86 conmeet the ports I69 and I10 with the opposite ends of the column clamping motor 42. The valve spool I16 is operated by the lever 92, suitable.

stopping mechanism I81 being provided for limiting movement thereof. No-centering spring is provided for the spool I16.

The port I66 connects through a fixed restriction I88 and a conduit I90 with a port I92 of a valve I94 for controlling operation of the head traversing motor 58. Valve I94 is provided with a pair of ports I96 and I98 which are normally connected with tank ports 200 and 202 when the valve spool 204 is in center position. Conduits 206 and 208, 2I0 and 2I2 connect the tank'ports I20, 202 and I12 and the tank ports H8, 200 and I14. When the valve spool 204 is moved upwardly, port I 98 remains connected with tank port 202 while port I96 is cut off from tank port 200 and connected with pressure port I92. When the spool is moved downwardly, opposite connections are made. Conduits 2I3 and 2, connect the ports I96 and I98 with the opposite sidesof the head traversing motor 58.

The valve I94 is provided with a pairof ports 2I6 and 2I8 which are connected together in center position of the spool and cut off from each other when the spool is moved upwardly or downwardly. Port 2I8 connects with' conduit I82 while port 2I6 connects with port I54 by a conduit 220. The valve I94 is also provided with a pair of ports 222 and 224 which are normally cut oil from each other in center position of the spool and which are adapted to be connected together when the, spool is moved upwardly or downwardly. Port 224 connects by a conduit 226 with port I56, port 222 connects by a conduit 228 with a low pressure pilot relief valve 230 adapted to dump oil to the tank 94 through a conduit 232 whenever a predetermined low pressure is exceeded in the conduit 228. Spool 204 is adapted to be operated by lever '88 and is provided with a centering spring 233.

The conduit 226 has a branch 234 leading to the control chamber 236 of a pilot operated relief valve 240. The latter is connected by a branch conduit 242 with the pump delivery conduit Vickers, 2,043,453. A high pressure pilot relief valve 246 connects by a conduit 248' with the con trol chamber 236 to limit the pressure .therein when the low pressure pilot valve 230 is cut off connected to conduit .252 when the motor 421s in unclamped position. The conduit 258 extends to a two-way pilot valve 260 which is operated by the arm clamping motor 50 through a lever 262.

branch I 64, and is adapted to dump oil to thetank 94 through a relief conduit 244. The valve 240 is constructed and operates similarly to the relief valve shown in the patent to Harry F,

The valve 260-opens communication between conduit 258 and a conduit 264 whenever the motor 50 is in clamped position, as illustrated, and closes communication therebetween at all other-times. The conduit 264 connects to the tank 94.

The pilot valve which is shown in Fig 2 is connected with an external source of pressure such as the customary air or water line by a conduit 266 and normally closes communication of that conduit with a conduit 260 leading to the operating cylinder 210 of a by-passing valve 212. The latter in its closed position cuts off communication of a port 214 with the conduit I26. Port 214 is connected to tank 94 through a conduit 216 leading to the tank conduit IIO. Whenever valve 80 opens due to excessive wear in the elevating screw mechanism the auxiliary pressure enters through the pipe 266, valve 80, conduit 258 to lift the valve 212 and connect the conduit I26 with the tank through port 214 and conduit 216, thus preventing the pressure from being applied to the head end of the arm clamping motor 50, and from being delivered to the arm elevating motor 60 through the by-passing valve I86.

In operation, with the parts in the rest position with the valves I06, I08, I94 and I68 centered, the oil delivered from pump 56 is by-passed through conduit 98, I64 and 242, relief 'valve 240 and conduits 244 and H0 tothe tank 94. The relief valve 240 is held open under these conditions by the fact that the control chamber 236 is. vented through a control circuit comprising conduits 234 and 226, ports I56 and I54, conduit 220, ports 2I6 and 2"], conduit I82, port I18, conduit 250, valve 254, conduit 258, valve 260 and conduit 264 to the tank 94. It will be noted that this control circuit may be blocked by movement of any one of the valves I08, I 94, and I 68 out of center position. The circuit is also blocked by the valve 260 whenever the motor 50 is in unclamped position, the reverse of that shown in Figure 5. When the circuit is blocked by the valve I68 the same may be opened again when the motor 42 completes its movement due to the two-way circuit from the conduit I82 to the conduit 258. I

If it is desired to elevate the arm-I6 on the column sleeve I4 the lever may be pulled forward, lifting the spools I28 and I48 simultaneously. Under these conditions pressure fluid flows from the pump through conduits 9.8 and I00. ports I04 and I24 and conduit I26 to the right hand end of the motor 50. The relief valve control circuit is blocked at the port I56 permitting valve 240 to close. The motor piston accordingly moves to the left in Fig. 5 or to the right in Fig. l,

releasing the arm clamps 46. The normal re sistance to this movement does not create suf-' ficient pressure in the conduit I26 to open the bypass valve I36. 3

As soon as the movement is completed, however, the piston stalls and pressure rises in the conduit I26 opening the by-passing valve I36 to permit oil to flow through port I38, conduit I40, ports I42 and I46 and conduit I52 to the motor 60. The latter is thus caused to rotate driving the nuts 60 and 16 in the direction to elevate the arm. The return circuit for fluid discharged from the left end of the motor 50 is through the conduit I34, ports I30 and H2 and conduit IIO to the tank. Fluid returning from the motor 60 passes through conduit I50, ports I44 and I20, and conduit IIO to the tank. When the arm has been elevated to the point desired the lever 90 is released permitting the valves I06 and I08 to center. At this time port I30 is opened to pressure port I02 of the valve I06 permitting pressure fluid to flow into the conduit I34 and to the left end of motor 50 returning the same to clamping position.

It will be noted that until the motor 50 reaches clamped position and the arm is clamped to the column the relief valve control circuit is not bypassed. If it is desired to lower the arm, lever 90 is pushed backwardly moving the spools H8 and I40 downwardly. Under these conditions pressure fluid is delivered from port I04 to port I22 and conduit I26 to unclanip the arm in the same manner as before. When the arm is fully unclarnped, the by-pass valve I36 again opens permitting pressure oil to flow through conduit I40, ports I42 and I44, and conduit I50 to the opposite side of the motor 60, causing the nuts 68 and 16 to rotate in the reverse direction, Fluid returns from the motor 60 through conduit I52, ports I46 and H8 and conduit IIO to the tank.

If it is desired to traverse the head I8 outwardly on the arm I6 the lever 88 is pulled forward, raising the valve spool 204 and permitting pressure fluid to flow through conduits 98 and I64, port I66, restriction I88, conduit I90, ports I92 and I96 and conduit 2I3 to the motor 58. Fluid returning from the motor 58 passes through conduit 2I4, ports' I98, and 202, conduit 206, port I20 and conduit IIO to the tank. At the same time the relief valve control circuit is cut oii at the port M8 and since ports 222 and 224 are open to one another the control chamber 236 on the relief valve is connected through conduits 234 and 228 to the low pressure relief valve 230.

It will be seen, accordingly, that when the motor 58 is operated the maximum pressure is limited to a lower value than that utilized for operation of the motors 50 and 60. Likewise, the rate at which fluid is supplied to the motor 58 is reduced by the restriction I88. It is thus possible to utilize a single pump 56 for the relatively light duty of traversing the head I8, as well as for the heavy duty of elevating the arm I8.

When it is desired to traverse the head inwardly the lever 88 is moved back, moving the valve spool 204 downwardly, permitting the pressure oil to flow from the port I92 to the port I98 and conduit 2I4 to the opposite side of the motor 58. Returning fluid passes through the conduit 2I3, ports I96 and 200, conduit 2I0, port H8 and conduit. Il to the tank.- The relief valve control circuit is again blocked at port 2I6 and ports 222 and 224 are connected together as before.

If it is desired to unclampthe column sleeve I4, the lever 92 is pushed backwardly, moving the valve spool I16 downwardly to admit pressure fluid from the conduit I64 through ports I66 and I69 and conduit I84 to the right hand end of motor 42. Fluid returning from the left end passes through the conduit I86, ports I10 and I14, conduit 2I2, port 200, conduit 2I0, port H8 and conduit IIO to the tank. The valve spool I16 not being spring centered, the control handle 92 may be left in its pushed-back position indicating that the column is unclamped. The relief valve con trol circuit is vented, however, as soon as the motor 42 completes its movement, the circuit being from the conduit I02 through port I80, conduit 252 and valve 254 to the conduit 258.

The column may be clamped by pulling the lever 92 forwardly, lifting the valve spool I16 and admitting pressure fluid from port I66 to port I10, conduit I86 to the left end of motor 42. Returning fluid passes through conduit I64, ports I69 and I12, conduit 208, port 202, conduit 206, port I20 and conduit IIO to the tank. The lever 92 may be left likewise in its forward position indicating that the column is clamped while the relief valve is again vented through port I18 and conduit 250 as soon as the motor 42 reaches clamped position.

Should excessive wear occur on the threads of screw 12 or nut 68, the valve opens, admitting pressure fluid to the piston 210 and opening the by-pass valve 212. With this valve 'open it is impossible to create pressure in the conduit I26 and accordingly, the clamping motor 50 cannot be unclamped nor can the elevating motor 60 be onerated since the by-pass I36 cannot open.

It will be understood, of course, that the speed of operation of the motors 58 and 60 as well as motors 42 and 50 may be regulated by opening their respective control valves to a greater or lesser degree.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a radial drill the combination with a rotatable column, an arm vertically slidable on the column and a head translatable on the arm of a fluid motor for clamping the column, a fluid motor for clamping the arm, means for elevating and lowering the arm, a fluid motor for causing operation of said means, means for traversing the head on the arm, a fluid motor for causing operation of the last said means, pump means forming a common source of pressure fluid for operating said motors, valve means for controlling operation of said motors and means for limiting the pressure efiective on the traversing motor to a lower value than the normal pressure on the elevating motor.

2. In a radial drill the combination with a rotatable column, anarm vertically slidable on the column and a head translatable on the arm, of a fluid motor for clamping the column, a fluid motor for clamping the arm, means for elevating and lowering the arm, a, fluid motor for causing operation of said means, means for traversing the head on the arm, a fluid motor for causing operation of the last said means, pump means forming a common source of pressure fluid for operating said motors, valve means for controlling operation of said motors and means for limiting the rate at which fluid is supplied to the traversing motor to a smaller rate than that to the elevating motor.

3. In a radial drill the combination with a rotatable column, an arm vertically slidable on the column and a head translatable on the arm, of a fluid motor for clamping the column, a fluid motor for clamping the arm, means for elevating a common source of pressure fluid for operating said motors, valve means for controlling operation of said motors and means for limiting thepressure effective on, and the rate at which fluid is supplied to, the traversing motor to values lower than the normal values for the elevating motor.

RAYMOND C. GRIFFTIH. 

